The present invention relates to an engine control apparatus and, more particularly, to an improvement of a response of an engine output adjusting means such as a throttle valve with respect to an operation of the accelerator.
Factors for adjusting an output of a vehicle engine include a fuel supply amount, an air-fuel ratio, and the like. A dominant factor for determining these adjustment factors is, e.g., an opening of a throttle valve in a gasoline engine. In a typical gasoline engine, the throttle valve is mechanically engaged with an acceleration pedal, and hence, the throttle opening is determined by a depression amount of the acceleration pedal. However, adjustment of the throttle opening by the mechanical engagement cannot allow adjustment of an engine output in correspondence with a change in operation state since the depression amount of the acceleration pedal has a direct correspondence with the throttle opening.
Along with the advance of electronics, an electronically controlled throttle controller has become popular. In this controller, the acceleration pedal is regarded as an input source of vehicle movement request information from a driver (operator), and the operation request of the driver is judged by the vehicle side on the basis of the depression amount of the acceleration pedal, so that an optimal throttle opening is determined considering the request and the output characteristics of the engine. The following conventional electronically controlled throttle controllers are known. As a technique associated with an improvement of reliability of a throttle controller, Japanese Patent Laid-Open (Kokai) No. 59-122742 is known. As a technique associated with an improvement of characteristics of a throttle opening with respect to a depression amount of an acceleration pedal, Japanese Patent Laid-Open (Kokai) No. 61-171846 is known.
Meanwhile, along with diversification of requrements on vehicles and the advance of electronics, an engine comprising of a supercharger such as a turbo charger, a vehicle with an AT (automatic transmission system) such as an electronically controlled automatic transmission system (to be abbreviated as an EAT hereinafter), a vehicle capable of setting a variety of operation modes such as power, normal, and economy modes, a vehicle comprising of an automatic drive function, and the like have been developed and are commercially available.
In an operation of the acceleration pedal, a driver depresses an acceleration pedal to accelerate a vehicle. Therefore, if the movement of the vehicle during acceleration is slightly greater from what the driver intended, the driver does not feel unease. However, when the driver releases the acceleration pedal to decelerate the vehicle, if the movement of the vehicle is delayed, that is, if the vehicle is not quickly decelerated, the driver feels anxiety. In particular, this tendency is conspicuous when the vehicle is decelerated from a high-load state during a low engine speed operation since a decrease in effective sectional area of an air intake path with respect to a decrease in throttle opening is very small.